Abstract

We investigated field screening mechanisms in large-aperture GaAs photoconductors, using an ultrafast pump–probe terahertz technique. After photoexcitation the bias field decreases to an intensity-dependent value as a result of near-field screening of the bias field. For longer delays the field exhibits an intensity-dependent decrease that results from a space-charge field caused by transport-induced charge separation. These measurements support recent theoretical results that the dominant saturation mechanism that limits terahertz output from large-aperture photoconductors is near-field screening of the bias field because the space-charge field develops on a much longer time scale than that of the terahertz pulse.

© 1997 Optical Society of America

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References

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  1. J. T. Darrow, X.-C. Zhang, D. H. Auston, and J. D. Morse, IEEE J. Quantum Electron. 28, 2291 (1992).
    [CrossRef]
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    [CrossRef]
  4. G. Rodriguez and A. J. Taylor, Opt. Lett. 21, 1046 (1996). In this reference the term “screening of the bias field by the generated terahertz field” was used to describe “near-field screening of the bias field.” Although the latter term, used here, more correctly describes the screening mechanism, both terms refer to the same mechanism: screening of the bias field by the near field generated by the photocurrent.
    [CrossRef] [PubMed]
  5. J. E. Pedersen, V. G. Lyssenko, J. M. Hvam, P. Uhd Jepsen, S. R. Keiding, C. B. Sorensen, and P. E. Lindelof, Appl. Phys. Lett. 62, 1265 (1992).
    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef] [PubMed]

1996 (2)

1995 (1)

L. Wang, W. He, G. Yang, and X.-C. Zhang, Chin. Phys. Lett. 12, 689 (1995).
[CrossRef]

1993 (2)

1992 (4)

J. E. Pedersen, V. G. Lyssenko, J. M. Hvam, P. Uhd Jepsen, S. R. Keiding, C. B. Sorensen, and P. E. Lindelof, Appl. Phys. Lett. 62, 1265 (1992).
[CrossRef]

P. N. Saeta, J. F. Federici, B. I. Greene, and D. K. Dykaar, Appl. Phys. Lett. 60, 1477 (1992).
[CrossRef]

N. M. Froberg, B. B. Hu, X.-C. Zhang, and D. H. Auston, IEEE J. Quantum Electron. 28, 2291 (1992).
[CrossRef]

J. T. Darrow, X.-C. Zhang, D. H. Auston, and J. D. Morse, IEEE J. Quantum Electron. 28, 2291 (1992).
[CrossRef]

Auston, D. H.

N. M. Froberg, B. B. Hu, X.-C. Zhang, and D. H. Auston, IEEE J. Quantum Electron. 28, 2291 (1992).
[CrossRef]

J. T. Darrow, X.-C. Zhang, D. H. Auston, and J. D. Morse, IEEE J. Quantum Electron. 28, 2291 (1992).
[CrossRef]

Benicewicz, P. K.

Bucksbaum, P. H.

Darrow, J. T.

J. T. Darrow, X.-C. Zhang, D. H. Auston, and J. D. Morse, IEEE J. Quantum Electron. 28, 2291 (1992).
[CrossRef]

Dykaar, D. K.

P. N. Saeta, J. F. Federici, B. I. Greene, and D. K. Dykaar, Appl. Phys. Lett. 60, 1477 (1992).
[CrossRef]

Dykaar, D. R.

Federici, J. F.

P. N. Saeta, J. F. Federici, B. I. Greene, and D. K. Dykaar, Appl. Phys. Lett. 60, 1477 (1992).
[CrossRef]

Froberg, N. M.

N. M. Froberg, B. B. Hu, X.-C. Zhang, and D. H. Auston, IEEE J. Quantum Electron. 28, 2291 (1992).
[CrossRef]

Greene, B. I.

P. N. Saeta, J. F. Federici, B. I. Greene, and D. K. Dykaar, Appl. Phys. Lett. 60, 1477 (1992).
[CrossRef]

He, W.

L. Wang, W. He, G. Yang, and X.-C. Zhang, Chin. Phys. Lett. 12, 689 (1995).
[CrossRef]

Hu, B. B.

N. M. Froberg, B. B. Hu, X.-C. Zhang, and D. H. Auston, IEEE J. Quantum Electron. 28, 2291 (1992).
[CrossRef]

Hvam, J. M.

J. E. Pedersen, V. G. Lyssenko, J. M. Hvam, P. Uhd Jepsen, S. R. Keiding, C. B. Sorensen, and P. E. Lindelof, Appl. Phys. Lett. 62, 1265 (1992).
[CrossRef]

Jones, R. R.

Keiding, S. R.

J. E. Pedersen, V. G. Lyssenko, J. M. Hvam, P. Uhd Jepsen, S. R. Keiding, C. B. Sorensen, and P. E. Lindelof, Appl. Phys. Lett. 62, 1265 (1992).
[CrossRef]

Lindelof, P. E.

J. E. Pedersen, V. G. Lyssenko, J. M. Hvam, P. Uhd Jepsen, S. R. Keiding, C. B. Sorensen, and P. E. Lindelof, Appl. Phys. Lett. 62, 1265 (1992).
[CrossRef]

Liu, Y.

Lyssenko, V. G.

J. E. Pedersen, V. G. Lyssenko, J. M. Hvam, P. Uhd Jepsen, S. R. Keiding, C. B. Sorensen, and P. E. Lindelof, Appl. Phys. Lett. 62, 1265 (1992).
[CrossRef]

Morse, J. D.

J. T. Darrow, X.-C. Zhang, D. H. Auston, and J. D. Morse, IEEE J. Quantum Electron. 28, 2291 (1992).
[CrossRef]

Park, S.-G.

Pedersen, J. E.

J. E. Pedersen, V. G. Lyssenko, J. M. Hvam, P. Uhd Jepsen, S. R. Keiding, C. B. Sorensen, and P. E. Lindelof, Appl. Phys. Lett. 62, 1265 (1992).
[CrossRef]

Rodriguez, G.

Saeta, P. N.

P. N. Saeta, J. F. Federici, B. I. Greene, and D. K. Dykaar, Appl. Phys. Lett. 60, 1477 (1992).
[CrossRef]

Sorensen, C. B.

J. E. Pedersen, V. G. Lyssenko, J. M. Hvam, P. Uhd Jepsen, S. R. Keiding, C. B. Sorensen, and P. E. Lindelof, Appl. Phys. Lett. 62, 1265 (1992).
[CrossRef]

Taylor, A. J.

Uhd Jepsen, P.

J. E. Pedersen, V. G. Lyssenko, J. M. Hvam, P. Uhd Jepsen, S. R. Keiding, C. B. Sorensen, and P. E. Lindelof, Appl. Phys. Lett. 62, 1265 (1992).
[CrossRef]

Wang, L.

L. Wang, W. He, G. Yang, and X.-C. Zhang, Chin. Phys. Lett. 12, 689 (1995).
[CrossRef]

Weiner, A. M.

Yang, G.

L. Wang, W. He, G. Yang, and X.-C. Zhang, Chin. Phys. Lett. 12, 689 (1995).
[CrossRef]

You, D.

Zhang, X.-C.

L. Wang, W. He, G. Yang, and X.-C. Zhang, Chin. Phys. Lett. 12, 689 (1995).
[CrossRef]

N. M. Froberg, B. B. Hu, X.-C. Zhang, and D. H. Auston, IEEE J. Quantum Electron. 28, 2291 (1992).
[CrossRef]

J. T. Darrow, X.-C. Zhang, D. H. Auston, and J. D. Morse, IEEE J. Quantum Electron. 28, 2291 (1992).
[CrossRef]

Appl. Phys. Lett. (2)

J. E. Pedersen, V. G. Lyssenko, J. M. Hvam, P. Uhd Jepsen, S. R. Keiding, C. B. Sorensen, and P. E. Lindelof, Appl. Phys. Lett. 62, 1265 (1992).
[CrossRef]

P. N. Saeta, J. F. Federici, B. I. Greene, and D. K. Dykaar, Appl. Phys. Lett. 60, 1477 (1992).
[CrossRef]

Chin. Phys. Lett. (1)

L. Wang, W. He, G. Yang, and X.-C. Zhang, Chin. Phys. Lett. 12, 689 (1995).
[CrossRef]

IEEE J. Quantum Electron. (2)

N. M. Froberg, B. B. Hu, X.-C. Zhang, and D. H. Auston, IEEE J. Quantum Electron. 28, 2291 (1992).
[CrossRef]

J. T. Darrow, X.-C. Zhang, D. H. Auston, and J. D. Morse, IEEE J. Quantum Electron. 28, 2291 (1992).
[CrossRef]

Opt. Lett. (4)

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Figures (4)

Fig. 1
Fig. 1

Experimental setup. HV, high voltage.

Fig. 2
Fig. 2

(a) Epeak versus pump–probe delay τ for photoexcited carrier densities from 3×1016 to 6×1017 cm-3. (b) Calculated values of Epeak versus τ.4 The bias voltage is 5  kV/cm.

Fig. 3
Fig. 3

Epeak versus τ for bias fields from 1 to 7  kV/cm and a carrier density of 3×1017 cm-3.

Fig. 4
Fig. 4

Epeak at a given pump–probe delay τ versus pump intensity for 50-µm-gap emitters5 (squares, τ=20 ps) and 5-mm-gap emitters (circles, τ=20 ps; triangles, τ=300 ps). The dashed curves are merely guides for the eye. The solid curve is the result of a calculation.4

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